Why is a male not allowed to listen to a female singing? Why is talking permitted?
The Talmud states, based on a verse in Shir HaShirim (the Song of Songs, 2:14), that a woman’s voice is to be considered Ervah, and should not be listened to except by males she has a close relationship with. This applies only to singing, not to talking. Perhaps this can be understood in the following manner:
Song is the language of the soul. The pleasure derived from song is not a physical pleasure, it is spiritual, like the pleasure derived from art. The pleasure we derive from music and art is a proof that an everlasting soul exists within the physical body.
A person who sings to another is "baring his or her soul"; a relationship is being developed between the singer and the listener. This may be even more true when the singer is female, because female souls are regarded as on a higher level than male souls. It is inappropriate for a woman to "expose" her soul in this manner to a non-related man, just as it is inappropriate for her to expose her body to anyone other than her husband.
This prohibition applies only when the male is attentively listening. If a male is in a room and a female starts singing, he isn’t obligated to leave; he should only try to avoid listening attentively, if possible.